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MD5 Collision Source Code Released
SiliconEntity writes "The crypto world was shaken to its roots last year with the announcement of a new algorithm to find collisions in the still widely-used MD5 hash algorithm. Despite considerable work and commentary since then, no source code for finding such collisions has been published. Until today! Patrick Stach has announced the availability of his source code for finding MD5 collisions and MD4 collisions (Coral cache links provided to prevent slashdotting). MD4 collisions can be found in a few seconds (but nobody uses that any more), while MD5 collisions (still being used!) take 45 minutes on a 1.6 GHz P4. At last we will be able to implement various attacks which have been purely hypothetical until now. This more than anything should be the final stake in the heart of MD5, now that anyone can generate collisions whenever they want."
So is SHA1 the recommended alternative?
Bradley Holt
(With sincere apologies to Bryce Jasmer.)
Carousel is a lie!
It's important news but not really that shocking. MD5 was not something professionals would recommend for a few years already.
Any half-way intelligent cryptographer would have suggested SHA-1, TIGER or perhaps HAVAL since quite some time already.
Tom
Someday, I'll have a real sig.
My desktop PC is a Pentium 4 at 1.5GHz, and even that thing is considerably slower compared to my 1.5GHz Celeron-M. A modern PC could crack it even faster.
"Beware of he who would deny you access to information, for in his heart he dreams himself your master."
Keeping in mind where MD5 is broken is important, so that good uses for this tool are not disposed of out-of-hand.
md5 is still good for keeping track of if your files have changed. It should not be used for document signing.
I'm essentially crypto ignorant. About all I've known to do was verify MD5 hashes on downloads. Now that this is by-and-large pointless, how to check the veracity of things like Linux ISO's, video drivers, etc, ad inifintum?
blarg.
Great. Now that MD5 is dead, the slow/theoretical attacks on SHA1 can be the focus of collision research. I look forward to changing hash algorythms again from SHA1 in a year. :-/
"Fight for lost causes. You may discover they weren't."
This is all really interesting theoretically, but who has the money to run a 1.6 GHz P4?
Recommended replacements are SHA (preferably SHA-2), WHIRLPOOL and/or RIPEMD.
http://en.wikipedia.org/wiki/SHA-2
http://en.wikipedia.org/wiki/WHIRLPOOL
http://en.wikipedia.org/wiki/RIPEMD-160
Why not just use 2 different algorithms? Yes, it's possible. Or hell, use 3. Can some one tell me why not this isn't a standard practice? Even if one has a weakness, you still have the other to back it up
I use HMAC-SHA-256 with PasswordMaker.
https://passwordmaker.org/passwordmaker.html
But will my insurance company cover the damage?
In other words, right now it's time to...
...LICK OUT THE KAMS, NOTHERGUCKERS!
doesn't bittorrent use md5 to verify the sections of files it has downloaded? will this facilitate poison seeds? or does BT use something more complex than md5?
I guess someone thinks he's a little too cool to comment his code properly. Yeah, like "/* B2 */" tells me anything useful you insensitive clog!
Hero of Allacrost, a FOSS RPG for *NIX/*BSD/OS X/Win
I think this will be the end of edonkey. AFAIK edonkey still uses md4 hashes. If it really is possible to find an md4 collision in a few seconds, I'm sure the MI will soon create a script that randomly downloads files, and reshares a collision.
Does this mean the RIAA/MPAA can poison torrents by generating files with the same hash?
How long till we see it integrated into cracking tools? Many Linux distros use MD5 for storing the passwords in the /etc/shadow file. How long will it take before they move on to SHA1 or Tiger or etc?
I wouldn't exactly call this source code... this gives almost no explination as to why it works, I could have gotten about as much knowledge from decompiling a binary of this.
this just means they can find more than one input that comes up with the same output it doesnt mean they can come up with an input to match a specified output (which can usually be protected anyway) so it really doesnt change much right? or am i missing something..
This new algorithm does not ruin the usefulness of MD5 hashes. The algorithm can generate two documents that have the same MD5 hash, an MD5 collision. But it can NOT generate an MD5 collision starting with an existing document. In practical terms, this means a file that has been signed with an MD5 hash is STILL secure. Nobody can replace the file with a different file that will have the same MD5 hash. However someone can prepare in advance two documents with the same MD5 hash and trick someone into believing one document is really the other. So if you trust the original source (a Linux distro for example) you can be confident you are downloading the original document.
- For the complete works of Shakespeare: cat
This more than anything should be the final stake in the heart of MD5, now that anyone can generate collisions whenever they want.
/.'d), but unless they have made an enormous breakthrough since this was last reported, this attack has very little implications for those of us who use MD5).
No, no, no. This does not allow an attacker to generate any collision they like. They cannot find data that collides with a piece of data I provide them with. All they can do is provide me with 2 pieces of data that happen to collide.
This means that an attacker can theoretically provide 2 different documents to people with the same hash, but they cannot easily produce a document that has the same hash as a document I have written.
(Disclaimer: I haven't actually been able to RTFA (it's
This program is an efficient way to generate two source blocks with the same resulting MD5. This program does NOT allow you to match an arbitrary MD5 hash. That may come some day, but unless I've missed a very important paper somewhere, it has not happened yet.
This does not totally invalidate MD5 for verification. This attack still does not let you poison a torrent feed, etc, unless you are the author of the original source data and you engineered the data specifically to be vulnerable to this attack.
This more than anything should be the final stake in the heart of MD5
No, no it won't be. It won't be, because MD5 is useful for many things where the existance of an "easy" (in quotes because easy is relative) method of generating colisions is irrelavant.
It won't even kill off the use of MD5 checksums as a signature for verifying authenticity, because if your data is smaller than the checksum there may not be a colision at all, and an exploit wouldn't matter.
This is an important discovery, but it doesn't make MD5 useless any more than CRC32 is useless.
OK, so clearly a scripted attack against MD5 is bad.
But aren't most people using MD5 using salted (as opposed to unsalted) hashes? (for those unclear on the difference, a "salted" has basically uses a local seed as part of it's MD5 hash, in addition to the value to be encrypted)
Doesn't seem likely that salted hashes can be easily broken by this technique, although clearly it's a concern that, should the salt value become known, all your passwords, etc, become breakable...
The only attacks that these md5 collisions allow are denial-of-service/destruction-of-data attacks, they don't generally allow the compromise of protected data or access to systems or suchlike. The collision blocks that are generated are effectively random data. It has yet to be shown how to -craft- a collision block.
/dev/random as out of a collision block.
If we could craft a collision block that contained a specified string at a specified position, that would be another issue altogether.
The ability to find collision blocks easily does suggest that crafted collision blocks might be possible, but for now, you have as good a chance of getting a viable exploit out of
This doesn't mean we shouldn't look to other options for the newest releases of high-security software, but it doesn't mean that the md5 algorithm should be purged from our systems altogether either. It's still extremely valuable at detecting accidental corruption, and useful-with-caveats at detecting malicious corruption (45 minutes to discover a block of data that matches the sum is not really useful in either speed or resulting data for any kind of man in the middle attack, for example, so using md5 to validate network packets is safer than using it to validate disk files).
Of course, the black hats may know more than we do about md5 weaknesses, but 'may know' is just as true of any other algorithm.
--Parity
'Card carrying' member of the EFF.
Just because collisions can be generated doesn't mean that MD5 is dead.
It might only take minutes to calculate two random strings with the same hash, but it would still take a very long time to calculate a second string that collides with a pre-existing string. So even though it is now cryptographically weak, it can still be used effectively to check the integrity of files.
Why not WHIRLPOOL (http://en.wikipedia.org/wiki/WHIRLPOOL), it is made by one of the makers of AES, Vincent Rijmen.
It is a hash algo. It's used not to protect the content of anything, just to provide a method to validate content integrity, to show nothing accidental or intentional happened to change it.
XML is like violence. If it doesn't solve the problem, use more.
(Coral cache links provided to prevent slashdotting)
Im sorry, you must be new here.
"In the game of life, someone always has to lose. To me, if life were fair, that someone would always be Oklahoma." -DKR
TIGER is good, as is Whirlpool. Whirlpool has the advantage that it uses AES as the basis, and AES is regarded as secure. It was also certified for secure work by NESSIE - a European group trying to do for the EU what NIST does for the US - which means that it's probably certified for use in secure environments in Europe.
According to the Hashing Function Lounge, there are other hashing functions that have not been broken (eg: cellhash and fft-hash) but these are sufficiently obscure that a lack of a known exploit may be through lack of study and not through the presence of good security. It would make them good for beating skript-kiddies, as they won't have the skills to find exploits and those skilled enough at finding them aren't studying those algorithms much. (I don't like security through obscurity, but technically these aren't obscured as anyone CAN study the algorithm.)
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
Maybe someone could explain why collisions are a serious problem for MD5. Or at least in what instances they are. I can see that in some cases, such as password hashing this could be a problem. But for many other uses I don't see what harm a collision has. Maybe I misunderstand but as I understand it MD5s are normally used in a checksum manner to sign or provide a fingerprint of a document. If you have an original document and compute it's MD5 then it can match some certified MD5 check sum. If someone were to generate a fake document they coul dnot design it to match the MD5 fingerprint. They could create some bit of gibberish that did match it but not a document that was useful as a forgery.
I guess if one were trying to deliberately pedal gibberish, like say if you were the RIAA trying to destabilize a torrent net then that would be all you care about. But for more general issues I don't get it.
Or is it now possible to generate a collision that also contains some intentional content like a binary program or source code or bank statement. That woul dbe be bad.
It seems like even in the case of gibberish generation that some simple hacks could extend the useful life of this. For example, if you were to MD5 a whole document and then MD5 the concatenation of every other byte in the document, it woul dbe pretty hard to find two collisions that had that property simulateously. Sure I wont doubt there are better ways to hash something than adding hacks to MD5. I'm just saying that it seems like a simple hack might well be good enough to extend its useful lifespan for passwords and file shareing.
But I invite you to explain to me why I'm wrong.
Some drink at the fountain of knowledge. Others just gargle.
great, will someone crack http://thedharmainitiative.org/ already?
$2$blah instead of $1$blah MD5 http://www.thkukuk.de/pam/pam_unix2/. Quite useful.
Filesharing networks that use MD5 hashes to verify a file would be severely affected. Companies like Overmind that spam the networks could use the collision to generate junk files with matching hashes. Then when clients start downloading, they'll get pieces of the broken file instead of the real one, causing the whole download to be corrupt.
If you get the error "error getting crypto context..." replace
if(!CryptAcquireContext(&cryptHandle, NULL, NULL, PROV_RSA_FULL, CRYPT_NEWKEYSET ))
with
if(!CryptAcquireContext(&cryptHandle, NULL, NULL, PROV_RSA_FULL, 0 ))
To actually run the program you have to convert your MD5 to four ints. Take your MD5, such as 098f6bcd4621d373cade4e832627b4f6
Divide it in four pieces and convert them to dec.
Hex
=======
098f6bcd
4621d373
cade4e83
2627b4f6
Dec
=======
160394189
1176621939
3403566723
640136438
Good luck.
This is bad, Now its only a matter of time before code like this is used to corrupt P2P networks whos primary file checking is based on md5 hashes.
So... When will MD6 come about? (yes, a weak version number pun, I know)
"I'm a well-wisher, in that I don't wish you any specific harm."
a very simple perfomance check i love to run on every computer i come across:
put windows calculator in scientific mode (to keep things comparable, please use windose calculator, not some custom written C+ program....)
type in 100,000
hit the n! button
ignore the warnings that it will take a long time, don't even bother clicking on "Continue", because the calculation is still going.
and report how long it takes to complete a factorial of 100,000
please report what CPU you have.
P4 3.2Ghz and Athlon 3200+ both do it in about 80 seconds....
So, not having read the FA, does this tool enable me to find collisions for different files *that are the same size*? or can I use size to discriminate?
This program generates ARBITRARY collisions. Given a tarball of a Linux kernel, you can generate some other file with the same MD5 hash. But can you generate a collision that is also a valid tarball that unpacks cleanly and compiles? The chances of that are so remote that I don't see it happening any time soon.
Here's the real trick. Take your kernel tarball X, and your hacked version Y. Using this collision finder, can you find some garbage Z such that Y appended with Z has the same hash as X? (Tar will, however, complain about extra stuff at the end of the tarball, but it would unpack and compile.) That's a MUCH harder problem than finding arbitrary collisions and would take a HELL of a lot longer to produce than 45 minutes on a PC.
Any half-way intelligent cryptographer would have suggested SHA-1, TIGER or perhaps HAVAL since quite some time already.
Actually collisions in SHA-1 were confirmed in February of this year, and refined in August. Any half-way decent cryptographer would be using SHA-256 or, better yet, SHA-384 or SHA-512. We've got the disk-size and bandwidth these days not to be worried about a few extra bytes. Bruce Schneier's initial article on this is instructive.
C'mon folks - yes there are plenty of uses for MD5 and yes MD5 is being used for a lot of applications now. However, it doesn't completely destroy its usefullness until we find a better replacement in the apps. Yes, 2 items can have the same hash - however it is unlikely to occur without trying to do it intentionally.
Remember the hashes, keys, doors, traps and such to keep unwanted folks from touching your data are only a way of keeping honest people honest. If you have honest people around - there is nothing to worry about.
It's the same attack that has already ben spoken about, just now it is available for the masses.
The scope of the attack is one can generate two files having the same MD5 sum, if he can have a random looking section in the middle of the file. i.e. possible in many binary formats but not possible in well formed ASCII text.
What the attack doesn't do is given a MD5 hash being able to find a byte stream that hashes to the same value. So passwords stored as their MD5 sums are still safe, you can't attack the RADIUS protocol with it and constructs like HMAC-MD5 used in SSL and IPsec are still safe. What you cannot trust anymore is for example the mechanism used to check distfiles on some BSD where the port system check the MD5 of the freshly downloaded archive. Nothing proves it is the same one that the porter used for the port (OpenBSD has been safe for a few years checking not only MD5 but SHA1 and RIPEMD, dunno for the other BSDs). And certificate authorities that don't modify the CSR they are submitted also are vulnerable to people forging certificates. Any serious CA won't be caught doing that mistake again.
One of the big lessons of these attacks on cryptographic hashes is : do not ever sign the hash of a document you didn't generate or at least modified (the document, not the hash).
This code is weak. I fired it up like 20 minutes ago and still haven't r00ted my box.
I know very little to absolutely nothing when it comes to encryption, so bear with me...
:-).
BUT I have a few sites where back in the day the easiest way for me to provide cross server verification was to use MD5 (one was a M$ Server and the other was a Unix box...we had a tool written in ASP and there were a few compiled components that are pretty blackbox or I would have ported the whole damn thing to PHP a long time ago...) But at the time MD5 was the only hash alg that I could implement in both without having to install all sorts of libraries (and for some reason, the standard crypto librariest STILL won't install on my PHP server -- I've taken to piggybacking off of a local MySQL server to do this these days...kinda horrible to call a query just to return an encrypted value...but that MySQL install isn't used as I have a dedicated box these days).
But back to the point, even then, I didn't feel MD5 was that secure...but I thought I had something that might work.
In session variables, I have several bits of data -- for instance, the email address. I use that I add a 64bit string of gibberish that is randomly rotated in a table on my two servers as a salt (say for the moment, this is secure
To get to my question -- given that only part of the data is ever given out to the user, how hard is it use this sort of algorythm to figure out the current salt I'm using?
I'm just wondering if this application will invalidate security protocol and if I will have to go back and revamp everything. Again, I know nothing, and I assume several folks that know nothing but enjoy talking out their ass will respond, so give me your best gibberish and I'll try to understand (I am, after all, a research scientist...I just know little about encryption and programming, but I can throw together crap just as well as any other monkey throw shit at the screen).
It can be used to generate two byte streams having the same hash, for some applications a big enough problem to render MD5 unusable.
rsync is one of many applications that makes use of md4 and md5. It uses md4 and md5 hashes as the final check to identify blocks don't need to be transmitted.
Dooooomed.
Question: Does this mean all my MD5 passwords for all my users can be cracked?
Answer: The short answer is yes, they can be cracked. The long answer is no, not if you used a salt, and the attacker has to get those md5 hashes first. You are not safe you are storing your user's password field input directly to the database ala the php/sql method of:
Question: How should I remedy this?
Answer: Always use a salt or salts. For example in the case above you could use this php/sql method instead:
Question: How/Why is this safer?
Answer: Collisions are only direct input for the md5 function to get the same md5 hash. So in the above case, $password was directly taken from the user and made into a hash. Assuming an attacker got an SQL injection in and grabbed the database, they could run this collision creator on a hash and produce an input that gave that exact hash.
But, this would be much more difficult with any code that introduced a salt. That is why the second code is better, it includes two salts that the attacker (through his SQL injection) is unable to account for.
http://www.crc2003.250x.com/ although old, is also interesting.
No one ever says, 'I can't read that ASCII E-mail you sent me.'
"Switch away from MD5/SHA1" to what?? SHA-256? Some AES-based hash? CRC-32?
MD5 is dead. SHA-1 is currently dying. They're both based on the same fundamental math, and the attacks on SHA1 are getting stronger and stronger. Now would be a really good time to get off of that entire family of hashes if you can (MD4, MD5, RIPEMD-* SHA-*, etc).
The crypto world is in a little bit of a bind when it comes to strong hashes now. We simply don't have any left that both have a long proven track record of analysis and haven't been seriously compromised. Best bet, IMHO, is to go with a new-blood hash algorithm. They seem to be the answer we're looking for - but of course what they lack is more years of intensive study by the experts for flaws they themselves might harbor.
So if you want to give them a whirl, I'd recommend looking at Tiger and Whirlpool:
http://en.wikipedia.org/wiki/Tiger_(hash)
http://en.wikipedia.org/wiki/Whirlpool_(algorithm
11*43+456^2
Are these entries for IOCCC or what?
MD5 may be useless for producing undeniable electronic signatures (proof that Alice generated and distributed a particular document, in the face of Alice's denials) but it is still quite useful for fraud prevention (proof that Eve generated and distributed a particular document, despite her claims that it came from Alice).
That is because the algorithm can produce pairs of documents that share a single hash, but that single hash is now known in advance.
Thus, Alice can use the algorithm to produce a pair of documents that have the same (unknown-in-advance) hash -- but, once Alice has signed a document with MD5, Eve still can't easily produce a document that has the same (known-in-advance) hash as Alice's original screed.
Ah! That's a very good point.
now if you you were a software company you could put torrents out (I assume they use blocks of MD5sum), and then after the torrent becomes popular start randomly seeding people with blocks that hash correctly but are complete garbage (since you can't pick what exactly you hash). if you do it right you would have games out there that would still mostly run. but would crash, or have garbled game data, etc.
I'm not sure if this is really all that useful. but this exploit certainly seems to make it easy to do.
“Common sense is not so common.” — Voltaire
Shit. I meant to type "...is not known in advance..." but instead typed "...is now known in advance...", completely reversing the meaning!
Most document formats have lots of "dead space", parts you can pretty much modify at will without changing what the user actually sees. Comments in HTML or PostScript. Old junk data in Word documents. Executables can have just about anything you like added if you know your stuff. The MD5 attacks currently available only 128 "dead space" bytes to generate a collision. So far from being a gibberish document, one can generate almost any document you want. This page has a simple example with PostScript files. Both files have the same MD5 hash, but one is a relatively harmless letter of recommendation while the other is a grant of security clearance. Get your boss to sign your letter of recommendation digitally, swap in the security clearance file, and pass it on. This is a Big Deal and a Major Problem.
Search 2010 Gen Con events
Actually this tool makes cracking linux user passwords using glibc 2.2. As this version of glibc using MD5 to encode in crypt function. It would only take matter of time to crack if an attacker get shadow file (or maybe passwd file on systems which shadow suite is not installed). There's no reason to use dictionary attack or something, just find collision text and use this text as login password.
I really find this extremely scary as there're lots of p0wned machines around now it will be easy for attackers to hide themselves (ie. they won't need to keep open port to be uidzero after first intrusion) Actually it's better to patch crypt function to use other more secure algorithms.
I downloaded the source, and took a quick look to make sure it wasn't really something intended to do something nasty.
I then realized that, going over it, it was a little like a Neanderthal trying to figure out how a swiss army knife worked... and just compiled and ran the damned thing.
I scanned over a good bit of the posts here, hoping for some info, and R'd a number of TFA's, but am not much closer to figuring out what I can actually do with this thing (or what collisions are for that matter). I'm even confused by it's parameters (you can pass it either four params or none at all. I'm not clear on what those params actually are for, or what the purpose in the default entries are).
Does anyone have a reference to some useful info that a caveman could understand, or shed some light on how this actually threatens my stylishly antiquated md5 shadow file?
We apologize in advance for any actual evolutionarily-challenged cave dwellers who may take offense at the above post.
Do not confuse "Freedom of Choice" with "Free Will".
anyone who uses an MD5 published on a ftp server or website for that is being seriously misled. a secure hash would have to be signed using DSA or RSA in order for it be meaningful (md5 hasn't counted as a secure hash in eons for that purpose) verified by its public key signed by trustworthy-to-you roots of trust. the .pub files you see on linux kernel downloads for example are exactly this pk signed secure hash.
the fact that you see people post md5s of things or do stupid things like include md5sum files in torrents (hello! bittorrent data is all identified and guaranteed by its SHA1s already) doesn't mean those people have a clue.
the md5sum file of a download is only useful as a final integrity check to make sure no bits were messed up going over the wire or more likely by your own cheap ass non-ecc ram, overclocked cpu, unstable kernel or lousy hard drive.
The Coral Cache is extremely slow. Please point the links to the original site www.stachliu.com/collisions.html as the html is small/static and the machine it's sitting on has a decent (100mb) connection. Thanks.
Now that the collisions are so easy to find, the RIAA will have a harder time (along with those bastards at BayTSP) proving that song downloaders have infringed. It's called "plausible deniability."
Or you may have a brain tumor...
The generaly accepted definition for "cracking a password" is, given the encrypted password, being able to generate a password the once entered in the authentication system will generate the same encrypted form.
For the second time, this attack does not permit that. This attack permits build two byte streams that hashes to the same value. So in a password context, assuming the password system permits the entry permits more than 1024 bits of arbitrary data to be entered as password (I don't remind the details well, but I think this is the amount of data that you must be able to change between the two streams) one could generate to "passwords" (being that long they don't qualify for this name anymore IMHO) that would hash to the same value.
How does that amount to an attack on MD5 passwords again? Never at any point the attack had been being able given a unknown to him MD5 hash to produce a stream that would hash to the same value.
unsigned int m0[32] = {
0x87472b83, 0x65d756a2, 0xfcfc845c, 0x13e3b751,
0x5641f279, 0x412fbde5, 0xc30f8345, 0xe7407b20,
0x06342d31, 0x625493ef, 0x7a949467, 0x55e92787,
0x87f390f9, 0x70af1e1f, 0xda1d3b84, 0xf943cfa3,
0x7e545b32, 0x1a120060, 0x3ba3a4d1, 0xfa5d29a0,
0x172bd4ba, 0x1d799f03, 0x26a81918, 0xc0c1f8d3,
0x74b4678d, 0xc744d004, 0x29464f42, 0x5de2c876,
0x47dac8d9, 0x1717cc87, 0x3d20a7bf, 0xa91ae3ce,
};
unsigned int m1[32] = {
0x87472b83, 0x65d756a2, 0xfcfc845c, 0x13e3b751,
0xd641f279, 0x412fbde5, 0xc30f8345, 0xe7407b20,
0x06342d31, 0x625493ef, 0x7a949467, 0x55e9a787,
0x87f390f9, 0x70af1e1f, 0x5a1d3b84, 0xf943cfa3,
0x7e545b32, 0x1a120060, 0x3ba3a4d1, 0xfa5d29a0,
0x972bd4ba, 0x1d799f03, 0x26a81918, 0xc0c1f8d3,
0x74b4678d, 0xc744d004, 0x29464f42, 0x5de24876,
0x47dac8d9, 0x1717cc87, 0xbd20a7bf, 0xa91ae3ce,
};
Your suggestion implies that you OS uses MD5 for crypt(2) [or crypt(3C)]. It does not. It uses whatever password hashing function your OS uses. So, it could be 3DES!
If you care about portability/repeatability, you'd be better off linking in OpenSSL.
Do daemons dream of electric sleep()?
IIRC SSL XORs an MD5 and SHA1 hash together and uses the resulting combined hash.
It doesn't. These programs generate two files which hash to the same value. They do not generate new files mapping to an existing hash. (There'll probably eventually be a way to do that, but not yet.) Your shadow file is safe, pretty much.
Signature.
For the impatient, here is a summary for my recommendations for 2005-2006:
See the paper for mode details.
chongo (was here)
"...which have been purely hypothetical until now."
Because source code hasn't been handed out to the public does not mean that any of this is "purley hypothetical." Much mathematical documentation has been released to the public on the subject.
They are still authenticating their ISO images with CRC... Maybe they should upgrade to MD5... (SHA-256 maybe too advanced for then...)/ install/
http://msdn.microsoft.com/vstudio/express/support
That Coral Cache link has gone from being slow to not resolving (for me).
even if you use this algorithm, it is likely to produce a bigger document. this fact can be used to in court to challenge. the only problem would be that someone has to find manually that the document has been forged. the second part could be that the forged document must not leave any signature of being forged (e.g. must not contain redundant data etc...). so yes, i would advise people not to use MD5 anymore, but I would still say it is okay to take some time and safely migrate to another algorithm rather than panic.
MD5 is only vulnerable if the attacker controls the documents.
Anybody can create two very different looking documents that have the same MD5 hash.
On the other hand, if you create a document with an MD5 hash it's VERY difficult for somebody else to could come up with a different document (gibberish or otherwise) that has the same MD5 hash.
IMHO MD5 collisions is a non-issue.
The described attacks would only work when you are dealing with active document types and only for the particular attack scenarios.
Because of the unfortunate properties of SHA-1, MD-5 like hash functionality implementations, if you find collisions x1, x2 such that hash(x1) = hash(x2) you can have the two different string x1||S and x2||S hashing to the same value, hash(x1||S)=hash(x2||S).
This is because these hash functionality is usually implemented as follows: start by hashing the first block (substring) of the string then take the output and hash it together with the second block, take the output and hash it with the 3rd block etc. If the first block of two different strings hashes to the same value while the rest of the string is identical you will get a collision. What these guys in Germany do is that they find a collision h(R1)=h(R2) (using the well known technique from China) enter it at the start of the ps document and then generate two different documents that look like this:
A || "if A == R1 present S1 else present S2" || S1 || S2 . The first document has A=R1 and the second A=R2. Obviously these documents differ only by A and because A hashes to the same value they both hash to the same value. Caesar sees the presentation of the document that contains R1, which is S1, he likes it and signs its hash. Alice takes this signed hash and presents it as the signature of a document that contains R2 and effectively. But this document prints S2 and Caesar does not like S2.
This is only usefull if Caesar is stupid enough to sign a document that looks like this. Of course, Caesar being aware that he runs an empire..., will for sure look at the source code of the documents he signs.
Some people also referred to the problem that arises with signing binaries or source code. As somebody else mentioned in this forum, in these cases you trust the signer and the trusted signer (e.g M$) would never create a binary or source code file that looked like:
R1 || "if A==R1 run good application else run virus" ||good application||virus. Even if the signer/coder was idiot enough to do it, you would still have to find R2 such that hash(R1)=hash(R2). In this case you should be able to find second pre-image of the MD5 hash, not a collision. Second preimage means, that given an y = hash(x) you can find x'such that y=hash(x'). Nobody has even come close to devising a technique for that.
If you could find second pre-images, you would be able to wreak havoc, for example by distributing fake Linux distros with the first block of the iso's being an MD5 second preimage of the valid distro.
In conclusion, I will still use MD5 and SHA-1 until they come up with a practical attack. I think these guys have had enough publicity for nothing already.
So, since the RIAA knows the SHA-1 hash and one plaintext "string" of (who's popular these days?) "The Attack of the WereChicken" (or was that cucumber?), does that mean better poisoning of P2P networks soon?
--LWM
unsigned int m0[32] = {
0x87472b83, 0x65d756a2, 0xfcfc845c, 0x13e3b751,
0x5641f279, 0x412fbde5, 0xc30f8345, 0xe7407b20,
0x06342d31, 0x625493ef, 0x7a949467, 0x55e92787,
0x87f390f9, 0x70af1e1f, 0xda1d3b84, 0xf943cfa3,
0x7e545b32, 0x1a120060, 0x3ba3a4d1, 0xfa5d29a0,
0x172bd4ba, 0x1d799f03, 0x26a81918, 0xc0c1f8d3,
0x74b4678d, 0xc744d004, 0x29464f42, 0x5de2c876,
0x47dac8d9, 0x1717cc87, 0x3d20a7bf, 0xa91ae3ce,
};
unsigned int m1[32] = {
0x87472b83, 0x65d756a2, 0xfcfc845c, 0x13e3b751,
0xd641f279, 0x412fbde5, 0xc30f8345, 0xe7407b20,
0x06342d31, 0x625493ef, 0x7a949467, 0x55e9a787,
0x87f390f9, 0x70af1e1f, 0x5a1d3b84, 0xf943cfa3,
0x7e545b32, 0x1a120060, 0x3ba3a4d1, 0xfa5d29a0,
0x972bd4ba, 0x1d799f03, 0x26a81918, 0xc0c1f8d3,
0x74b4678d, 0xc744d004, 0x29464f42, 0x5de24876,
0x47dac8d9, 0x1717cc87, 0xbd20a7bf, 0xa91ae3ce,
};
real 49m56.628s
user 44m52.036s
sys 0m5.060s
Actually...
Regarding security through obscurity, I think your comment shows a rather common misconception, namely that every kind of obscurity that might be construed as improving security (rightfully or not) is automatically bad, and (as a corollary) that security through obscurity is automatically bad.
I don't think that's true, though. Security through obscurity is not real security, but and you should never rely on it - never alone, of course, and also not in conjunction with other security mechanisms -, but that doesn't mean it can't be useful.
It's doubtful that it would be in the case you mention, of course - obscurity, for hash functions, cryptographic algorithms etc., usually just means that they aren't well-studied (at least not as much as others) and might have weaknesses nobody has found yet, but in *general*, obscurity can provide an additional deterrent against attacks that can be useful, especially in real-world applications where not everything is black and white.
Here's an example: a few years ago, I was running the SSH server on one of my computers on a non-standard port. From a theoretical point of view, that doesn't change anything: somebody doing a port scan would still find it easily, so if a weakness were found in SSH (the protocol) or OpenSSH (the implementation), my server would've been just as vulnerable as any other server out there. But still, if a script kid had decided to take a tool that scans for vulnerable SSH servers and roots them, mine probably would've escaped; and the constant password brute-forcing attempts from Asian IPs stopped as well. So while using a non-standard port was utilising obscurity, it did make me more secure, in real-life terms (even though the same wasn't true in terms of theoretical security).
How does this apply here? Not at all, really, as I said above - you're better of using a well-tested hash function like SHA-512 (why restrict yourself to SHA-256? The extra bits will keep you safe for a little longer when SHA-256 is broken - and it *will* be broken, eventually) than an obscure hash function that noone ever heard about.
But the automatic reaction that IT professionals seem to have that obscurity is *always* bad is rubbish. As long as you don't rely on it (that is, as long as your system would still be secure even if the obscurity were gone), it's not only not bad, but in fact can be a valuable tool.
Just food for thought.
quidquid latine dictum sit altum videtur.
A hash function is essentially a very lossy compression algorithm. Because it's lossy, there is no way to recreate the original file from the hash; thus, it is trivial to prove that there are multiple original files matching the same MD5 hash. Doing this in a brute force fashion may be easy to implement, but it would definitely be time consuming (for the CPU, anyway). What's truely fascinating here is that you can approach this from from the more "elegant" direct method; thus allowing the potential "masquerading" of malicious information as being legitimite. This is great work, even if it adds no real value (since it effectively breaks a working standard).
On a side note, I sure hope there aren't any standing copyrights on MD5; otherwise, this work will be quashed by the DMCA in short order, and we'll have to revert to printing this code in tiny print on t-shirts like we did DeCSS
# They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety. --Fran
I've been throwing around for a while the idea of doing the same for crypto references the same thing that OS groups have done with well-known port numbers - have a standard list of names/numbers that everyone can refer to, so that swapping between implementations is easier and multi-toolkit packages don't have to have lots of complicated mangling to figure out who refers to what how.
I've also been throwing around the idea of getting popular toolkits (such as SSL, the shadow password suite, etc) to have the ability to use some popular crypto library as an alternative to their internal functions, precisely so that users can update to new algorithms quickly and easily. It would seem to make a lot more sense than the existing approach.
Finally, I've been proposing a much more standardized internal API so that whenever NIST or NESSIE or someone else runs a crypto contest, the example functions can be directly uploaded into the crypto libraries so that people can experiment with them, so that we can see what happens when you REALLY turn a lot of eyes onto these algorithms.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
That's not correct, in general. The fact that "multiple strings may resolve to the same hash" is a given, with any hashing system, because the number of bits in the original is larger than the number of bits in the hash, so there are more combinations of strings than there are of hashes, therefore "multiple strings may resolve to same hash".
This exploit makes it possible to generate collisions, but as the OP points out, that doesn't help you in the password hashing case since you don't know the text that you're trying to generate a collision for, and in any case, it seems the algorithm doesn't let you pick your source text.
If the current result somehow shows that MD5 suffers from more collisions than other hash algorithms, then that might make it "some percentage easier to violate" than was previously known to be the case. As it is, the weakness of MD5 for password hashes doesn't seem to have been demonstrated.
I'm currently using the following ID for my files: md5(filecontent)."-".length so it gives something like 1a566e4f3293bc8739113457634128b5-cb451. So am I safe? What is the probability to have two files with the same MD5 and the same length?
Million Dollar Screenshot
Uh.
...Are all still safe.
My understanding is that Tiger has not undergone the degree of review that MD5 and SHA1 have. I've never heard of HAVAL.
My vague understanding is that what the people here have done is made slightly more convenient an *extremely* limited specific attack based on a collision that someone else discovered. Basically, in my understanding, if you start the file/bitstream/whatever that you are hashing with their particular special block, they have a tool that can generate a bitstream that collides with the first one. However, it's pretty unlikely that anyone is going to have a file that actually starts with this block, unless they're trying to demonstrate the collision.
Now, this is interesting for cryptographers, because there's a few things that were safe to do before that aren't any more. The big one is you can't have a system in which Person A hands Person B a file (of unconstrained content), which Person B then MD5 hashes and signs the hash of and returns to Person A. However, things like:
* Passwords hashed with MD5
* P2P files addressed with an MD5 hash or hash tree
* Linux isos
The Slashdot article seems to be mostly frightening because the submitter, "SiliconEntity", is misleading Slashdot readers in an attempt to have a more exciting story.
Any program relying on (nontrivial) preemptive multithreading will be buggy.
Why would someone first put up a torrent and then poison it with bad blocks?
**AAs are interested in poisoning data they did not publish themselves. They cannot make the uploader use blocks they have collisions for.
* shrug *
On se Internetz nobody noes your German.
If TCP were to be redesigned today, it would most probably have a 32-bit cyclic redundancy check specified as an error check instead of the current checksum.
In the IPv6 stack, is TCPv6 identical to TCPv4?
A friend of mine has been running http://www.md5lookup.com/ for quite some time, and has been working on generating the hashes as fast and efficiently as possible.
:)
!!!Conceptual Blathering Below!!!
Projects like this are a major threat to the "security" of the internet, given the fact that MD5 is still widely used. However, I am of the belief that the concept can be turned around and used to optimize the transmission and storage of large files. Granted, there is a lot of legwork for the CPU required, I have had the idea for the last year or so that it would be possible to transmit a small hash and control string, and build a large file from it. Imagine downloading a Slackware ISO in under 5 seconds, and building it in n seconds!
For one, it would solve the problem of network latency and load, because there would no longer be any massive chunks of data being transferred.
Second, it would allow individuals with slower internet connections (dialup, slow DSL, etc.) access to content they never dreamed possible.
Third, it would just flat out be cool.
I realize that it would take a lot of computing power to rebuild a file from a simple hash, but which would you rather have?: A 4+ day wait to download a DVD image or a ~1 hour wait to build the file?
So, now someone can make some garbage with the same md5 summ as a file, we want to dowload, he may destroy everything. Yeah, that can become a problem, but the solution is really easy.
Our P2p Programms then just have to use multiple kinds of Hashing Algos. So maybe someone can make garbage with the same md5 summ like our file and someone may be able to make a file with the same hash summ that algorithm b produces. Same for hash algorithm c.
But i think it`ll be ALMOST impossible to make one garbage File that makes an identical Hash summ like our file with md5,b and c!!!!
And for verifying whether a file was transferred correctly from an official server, for that md5 will still be usable. Almost impossible, that we get randomely the same md5 summ.
Our P2p Programms then just have to use multiple kinds of Hashing Algos. So maybe someone can make garbage with the same md5 summ like our file and someone may be able to make a file with the same hash summ that algorithm b produces. Same for hash algorithm c.
But i think it`ll be ALMOST impossible to make one garbage File that makes an identical Hash summ like our file with md5,b and c!!!!
The main problem with MD5 as it's used today comes when MD5 is used as a component of a digital signature scheme. Most digital signature schemes based on public key crypto work like this:
To verify a digital signature, the following is performed:
Now, it's easy to see why this spate of collision attacks on hashing algorithms is so deadly. If, given some signed document, you can produce another document that verifies to the same signature, well, I guess you're in a world of hurt. If these documents happen to be public key certificates, well, the whole PKI more or less collapses. And well, here's a bit of news: someone has done just that with X.509 certificates based on MD5.
Qu'on me donne six lignes écrites de la main du plus honnête homme, j'y trouverai de quoi le faire pendre.
The parent comment, which I wrote, was based on a severe misunderstanding of the extent of the capability of the attack. In particular, I didn't realize that the attack could find collisions even with arbitrary, attacker-specified IVs. What that means is that it is indeed possible to generate x.509 certificates containing different keys but the same MD5 hash (and therefore the same signature). In fact, it's been done.
Note to ACs: I usually delete AC replies without reading them. If you want to talk to me, log in.
A lot of people have the programs md5sum and sha1sum installed, but they often don't have equivalent programs for the SHA-2 family. To calculate those you can use the command:
or you can download a dedicated program: http://www.ouah.org/~ogay/sha2/.
There's a hidden treasure in Python 3.x: __prepare__()
Calculator.app on Tiger on my PB 1.5GHz is clearly superior to all these other results because:
1) The answer returns immediately. None of this waiting around crap.
2) The answer is "Infinity", which goes to show that OSX can handle much bigger numbers (Infinitely bigger!) than other OS's.
No wonder AAPL is soaring.
Is it advised to switch GnuPG from SHA-1 for signatures to SHA-256 (like immediately)? How can I make this configuration change?
Rnfl Xnezn!
In Soviet Washington the swamp drains you.
(from material at the Pure Crypto Project - http://senderek.de/pcp/ )
Quote below from http://senderek.de/pcp/pcp-security.html
The nice thing about Adi Shamir's hash function is that it, as well as the RSA cryptosystem co-created with Rivest and Len Adleman is all based on simple modular exponentiation.
Too bad the Feds consider arbitrary precision mathematics used for encryption purposes to be 'a munition' and 'a controlled export'....
Years ago, they raked Phil Zimmerman over the coals over his email cryptosystem PGP then (eventually) left him alone.
Can't cryptosavvy individuals secure the details of their affairs with strong encryption WITHOUT being hassled by 'the Man'?...
P.S. However, Rivest came up with a scheme that gives you 'confidientiality *without* encryption' through a scheme he calls Chaffing and Winnowing
Enjoy!
Because that would require the hashed password and a preimage attack.
See here.
Summary for those who are lazy:
In conclusion, the value of this attack/exploit is only relative to how the hash function is used in an application. Just because this exploit and source code for it exists, that does not that these hashing algorithms are completely useless.
MD5 may be dead for security reasons, but it's still great for reliablity checksums where no malicious activity is provided.
Yesterday a guy sends me an order, the project is in Corel 12. But he knows I have Corel 9 only, so 2 minutes later he sends another mail, "corel 9 replacement".
But the new file won't open.
md5sum file1.cdr file2.cdr
"Excuse me sir, but you have sent the same ver.12 file again."
It's still a great hashing/checksum algorithm and it will still work in all the situations where no malicious activity is involved.
Anagram("United States of America") == "Dine out, taste a Mac, fries"
There are three things we are talking about:
1 ) Finding a collision is one piece of the puzzle. How to exploit it?
Lets say you are hosting 'happy frappy firefox downloads!' and you are helping spread firefox, yet your version contains some nast13z malware.
Is this a situation where a MD5 hash collision will help you? Probably not - simply changing the file, yet publishing the original MD5 next to it, and very few people will check. The file size will usually give you away, even if one BYTE changes.
Someone mentioned empty space in files to help generate a collision.
So we take two different files, and we try and get the first file to collide with the second file (THIS IS NOT WHAT THIS CODE DOES!).
Also has this been benchmarked on larger files? File that may in fact be targetting (software installs?) Or is this not for that?
3 ) The next is password hashes. My password for slashdot it fr4pp4l1fe. The hash is stored on slashdots server.
Well done. Now, as long as the hashes are safe, then I am safe. If someone could easily find another password that hits that, then I am scr3w0r3d!
Now usually anyone can lookup password hashes (or I have been able to do this in systems I have been in...) and regularly passwords in databases are reset by a dbadmin using a simple PLSQL like : set passwort = leetShizzle('monday').
Collisions do pose a threat (how much of a threat?) for passwords. Knowing the hash you can find another input. Not the original.
2 ) Poisoning torrents.
You can poison torrents by writing a maliscious client that returns shitty data. However, with hashes, a node will verify the data you are passing with a hash function - after receiving it. If the has failed, it will assume a broken packet that wasn't caught with CRC or a bad client.
Collisions allow certain files to be pre-loaded with poisoned content, yet look like the original. Because original files are large, the whole files cannot be passed around for nodes to check the fidelity, since they are fact being downloaded anyway (if that makes sense).
Hashes breakable means different code can be sent. However, will a length check thwart this?
Do clients hash every block of data?
please type the word in this image: gruesome
random letters - if you are visually impaired, please email us at pater@slashdot.org
#hostfile 0.0.0.0 primidi.com 0.0.0.0 www.primidi.com 0.0.0.0 radio.weblogs.com
Faster than brute force?
What makes it so? Can someone explain in english? Looking at the code I couldn't really get a flavour of why this is faster than brute force.
Thank you.
Bungle.
#hostfile 0.0.0.0 primidi.com 0.0.0.0 www.primidi.com 0.0.0.0 radio.weblogs.com
although clearly it's a concern that, should the salt value become known, all your passwords, etc, become breakable...
...and this is why anybody who implements salt generates a unique random salt for *each* password, not one system-wide one.
You can accomplish anything you set your mind to. The impossible just takes a little longer.
And a bad one at that. Better use MD5(secret input secret2) or even better use a properly defined one like HMAC if what you want is a MAC.
There is an attack on this construction as well.
Please people, stop proposing constructions if you aren't a cryptographer.
-Matt
I have collected many posts regarding this issue on my blog category on MD5. And posted my practical exploit of MD5 some time ago on slashdot. This new code is the tombstone for MD5, in fact, now we can write a better exploit of MD5, for example, someone can attack a mirror site of apache, that uses MD5 as check sum, and replace a distribution of the software with some time of malware.
hey, does your P4 have Hyper-Threading? i've heard of it doing strange things; sometimes my friend's 3.0GHz with Hyper-Threading machine will play mp3s twice as fast! (can't remember what player he was using though.)
i disable sigs